THE LOBSTER. 



143 



sac, or pericardium, thence through the little valves into 

 the ventricle (Fig. 120). The blood is next forced 

 into the large tubes, or arteries, by the contraction or 

 squeezing of the ventricle, as in the mussel's heart. 

 When the lobster is out of the water the ventricle beats 

 about thirty times a minute, but it beats much faster 

 when in the water (about fifty times a minute). After 

 the blood has been deprived of oxygen, it moves slowly 

 and the amount of carbonic acid it contains makes the 

 lobster insensible. You know, if you stay in a room 

 where the air is bad, you feel yourself getting sleepy. 

 You and the lobster are in a state of what is called 

 asphyxia, meaning without a pulse. 



The lobster's blood is colorless when living, but 

 when dead it makes a purplish clot. The blood-cells 

 look much like the human amceb^e ; they are colorless, 

 contain little grains, and show the same crawling move- 

 ments. The lobster will bleed very freely with only a 

 slight wound, because the blood-vessels are so wide and 

 loose. One might think he would bleed to death when 

 he so carelessly throws off his limbs ; but the lobster is 

 a good surgeon, he always takes care to cut off, or am- 

 putate, at a joint where the vessels are narrow, and 

 when he gets wounded in a limb he amputates it at the 

 joint above the wound. The joint acts as a surgeon's 

 bandage and soon stops the bleeding. Thus surgeons 



